The rhythmic pattern of activation in flexor and extensor muscles that occurs during walking is generated at the spinal level in a number of animals. However, supraspinal centers in the brain coordinate, modulate and adapt this pattern to produce effective locomotion. The role of ?higher centers in walking and the properties of pattern generating circuits in the spinal cord have been extensively studied to understand locomotory deficits in chronic spinal cord injury and Parkinson?s disease. An examination of the cellular properties of individual neurons in the spinal cord is limited in vertebrates because it is difficult to identify and to record from single nerve cells. Insects provide a model system, with limited walking circuits and identifiable neurons, to address these questions. In this proposal, three specific aims will be developed. 1) The physiological characteristics of leg motoneurons in cockroaches that lack input from the ?higher? centers will be examined using intracellular recording techniques. The changes in neuronal properties with the addition of pharmacological agents and tonic electrical stimulation will also be characterized in behaving animals. 2) A preparation in which activity from the head ganglia can be reversibly blocked using a sucrose solution will be utilized. This preparation will allow for neuronal activity to be recorded in a preparation that does not walk (neck connectives blocked) and one that walks continuously (circumoesophageal lesion). 3) Changes in walking behavior and neuronal properties in cervical lesioned cockroaches over time and with step-training will also be examined.